A capless refueling system provides numerous benefits to both the vehicle and vehicle operator. There is no risk of losing a refueling cap, of improperly replacing the refueling cap following a refueling event, or of stripping the threads of the refueling cap so it cannot form a complete seal. Any of these conditions may lead to an increase in evaporative emissions from the fuel tank, and may further prevent the vehicle from properly performing evaporative emissions leak tests.
One configuration for a capless refueling assembly includes an upstream door and downstream door that are biased closed by preloaded springs, sealing the fuel tank from atmosphere. The doors are forced opened sequentially when a refueling nozzle is inserted into the refueling assembly, and close upon withdrawal of the refueling nozzle.
However, residual fuel may be released from the refueling nozzle during withdrawal, and may become trapped between the upstream door and the downstream door of the refueling assembly following a refueling event. An increase in ambient temperature may cause the trapped fuel to vaporize, creating a positive pressure between the upstream and downstream doors. During an evaporative leak check module (ELCM)-based leak detection test, the vacuum drawn on the fuel system may, in conjunction with the positive pressure in the refueling assembly, be strong enough to force the downstream door open, which may in turn lead to a false-fail diagnosis.
The inventors herein have recognized the above problems and have developed systems and methods to at least partially address them. In one example, a method for a vehicle, comprising: following a refueling event, venting a capless refueling assembly to a fuel tank; and then executing an evaporative emissions leak test. In this way, residual fuel trapped in the capless refueling assembly may be removed. This, in turn will prevent a pressure build-up in the capless refueling assembly which could lead to the downstream door opening during a leak test, thereby confounding results.
In another example, a system for a vehicle fuel system, comprising: a fuel tank comprising a capless refueling assembly; a fuel vapor canister coupled to the fuel tank via a fuel tank isolation valve; a vacuum pump coupled to the fuel vapor canister via a canister vent valve; a controller configured with instructions stored in non-transitory memory, that when executed cause the controller to: following a refueling event, open the fuel tank isolation valve; open the canister vent valve; activate the vacuum pump to draw a vacuum on the fuel tank without checking for a leak; and then draw a vacuum on the fuel tank to check for a leak. In this way, the venting mechanism of the capless refueling assembly may be used to clear residual fuel from the assembly following a refueling event and/or prior to a leak test. Thus, no additional hardware or expense is necessary to realize this system.
In yet another example, a method for a vehicle, comprising: following a refueling event, opening a fuel tank isolation valve; activating an evaporative leak check module pump; drawing a vacuum greater than a threshold without checking for a leak; and then drawing a vacuum to check for a leak. In this way, an evaporative leak check module based test may be made to be more robust and more accurate, with fewer false-fail results. This, in turn, may lead to a reduction in in-field warranty service, and accordant savings to the vehicle manufacturer.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.